Reductions in the cost of image-based modeling software (also known as
photogrammetry), 3D cameras, and digitizers will make it easier than ever
to create accurate models of existing objects.

3D cameras and digitizers are good
for small objects, but they are sometimes difficult to use for large objects,
like buildings. High costs for the hardware have traditionally limited
these technologies to big studios, but prices have been coming down.

The picture to the right is of a MicroScribe-3D digitizer that can be
used to model objects up to 66" in size. This type of technology
has been used in many applications, including Disney and Pixar's Toy Story.
Watch the Ultimate
Toy Box DVD set to see how Pixar used this technology.

Image-based modeling software has been around for a number of years.
Recently the technology has matured enough to be considered for mainstream
applications. With these programs no artistic talent is needed to create
very detailed models. Just snap pictures of the object you wish to model,
assign common reference points in software, and let the program analyze
the photos to create a model. Image-based modeling works with any object.

[Update 2010] As time goes on software gets more advanced and it's now possible to create 3D models without assigning reference points. Agisoft PhotoScan and its free little brother StereoScan are two such programs. PhotoScan takes in multiple images as input, aligns them, and outputs a 3D model in one of many formats.

While image-based modeling technology can work with any object not all
of the products do equally well. PhotoModeler,
for example, works well with architectural objects, but it is not as efficient
for modeling organic objects, like people.

This is because PhotoModeler requires users to
manually assign reference points for areas that can be seen in multiple
images. Each of these reference points form a vertex in the final model.
Because organic objects require a lot more vertices than inorganic objects
the sheer number of reference points needed to create a quality model
increases development time dramatically. Also, it is often difficult to
accurately identify points that are present in multiple images when there
are no sharp edges to use for reference.

A couple of products use different methods to tackle the problem of modeling
organic objects. Eyetronics
ShapeSnatcher uses a grid, which is shined on the object from a slide
projector, to automatically align the images and create a model. The grid
is not part of the texture.
D Vision Works Limited uses reference points to align the photographs,
but the actual model is processed automatically. The user needs only to
draw an outline around the object in the D Sculptor software to help make
the processing easier.

The downside to this approach is D Sculptor seems to require more photographs,
than other programs, to create a model. This isn't really much of a downside
though because reference points for complicated organic objects would
probably still take longer. Some types of objects will not work well with
this method. You quickly can test how good this method is for your object
by turning the model 360° and studying the outline of the model. If
a lot of details are hidden by the outline then this method of image based
modeling might not be right for you. Strata Foto3D and iModeller 3D are other applications that seem to use the masking method.

It should be mentioned that PhotoModeler and some other reference point
modelers are so accurate for architectural models that they can actually
be used to obtain detailed measurements of the objects. This makes these
programs extremely useful for architects and engineers.

Some products are designed specifically to create models of faces and
characters. Two are Cyberextruder
and 3DMeNow.
Cyberextruder creates a model from just one photograph while 3DMeNow requires
two. 3DMeNow should give better quality models, but those from Cyberextruder
should be just fine for games like Quake 3 and The Sims. 3DMeNow can also
animate the model using one of 35 actions. The Pro version can output
the model and animation data to programs like 3ds max and Maya. It even
includes morph-targets for facial animation and lip-synching applications
like LIPSinc VentriliquistT.

The products mentioned above have all been software packages that must be installed on your computer. Scanetica has taken a different approach by creating a web service. It doesn't require any special equipment or software and for now at least (Feb. 2009) it's free to use. The service can handle a wide range of subject sizes from satellite imagery to tiny fossils.

Ironically, image or object based modeling gives new life to traditional
art forms, like sculpting. Once an object is sculpted it can easily be
converted into a computer model.